1. Field of the Invention
The present invention generally relates to control and, more particularly, to a control apparatus including a lower layer control unit that performs control of a load, an upper layer control unit that controls the lower layer control unit, and a communication line that performs communication between the upper layer control unit and the lower layer control unit.
2. Description of the Related Art
In conventional image forming apparatus, a plurality of loads have been driven and controlled with one controller. However, along with an increasing scale of apparatuses and loads, wiring between a controller and loads increases and becomes complicated, thus operating cost tends to increase.
Thus, a configuration in which a plurality of slave controllers for driving and controlling loads arranged in a distributed manner in the vicinity of the loads, and these slave controllers are controlled by a master controller, is discussed in Japanese Patent Application Laid-Open No. 11-163885. Japanese Patent Application Laid-Open No. 11-163885 further discusses that in an apparatus in which the corresponding load is controlled by the slave controller that has received a load control request through serial communication from the master controller, the slave controller, when detecting a communication error between the master controller and thereof, perform control to stop the load.
However, the slave controller can autonomously stop the load at the time of trouble, whereas the master controller side cannot know the cause of the trouble.
Even if the master controller could recognize occurrence of communication error, communication error occurs when noise is mixed into a communication line, and in addition, occurs when there is abnormality in power supply voltage to the slave controller. As a result, the master controller cannot recognize its detailed cause. For this reason, the master controller cannot display the detailed cause of the error on the display unit at the time when an error occurs, and the service person or the like spends much time in tracking down the detailed cause of the error.